A typical arrangement in fluid pumps, such as liquid ring pumps, is to employ mechanical seals for replacing packed glands and lip seals. Mechanical seals are provided to prevent pumped fluids from leaking out along the drive shafts. However, in known fluid pumps, a common problem is mechanical seal lifetime, which naturally influences the reliability of the fluid pump. Particularly in vacuum sewage systems where the flow of sewage is very turbulent the mechanical seal normally runs in very dry conditions, whereby the mechanical seal is subject to high risks of damage.